This invention relates generally to the location of tubular members one within another. The invention has particular, but not exclusive, application to the location of casing and tubing hangers within wellhead housings.
In the formation of wells for the extraction of oil or similar materials, it is the usual practice to run a series of concentric casings and tubings through a wellhead housing into a borehole which extends to the source of oil or other material. The casings and tubings are supported on hangers which are themselves carried within the wellhead housing. A first casing hanger usually rests upon a shoulder formed in the wellhead housing and subsequent hangers are stacked upon that casing hanger.
One way of stacking casing and tubing hangers on top of each other within a wellhead housing is to provide each hanger with a flat or square landing shoulder on which a corresponding flat surface of a subsequent hanger can land. Flat landing shoulders however have been found to be unacceptable, because they encourage the build-up of debris on those flat surfaces and this can lead to slight tilting of the hanger when it lands together with other problems such as an increased stack-up height. One way of avoiding debris build-up is to provide tapered hanger landing shoulders so that debris cannot settle easily on those shoulders. However, when tapered or conical landing shoulder are used subsequent hangers spigot into each other and hence tend to align both laterally and angularly with the hanger on which they are resting. Thus, any misalignment of a lower hanger tends to be amplified through the stacked hangers and this can lead to problems, particularly in connection with the sealing of upper hangers within the wellhead housing. Also where a Christmas Tree or tubing head adaptor is fitted to the top of a wellhead housing, it is usually necessary for this equipment to connect with a hanger which is as concentric as possible with the wellhead housing.
The H. K. V. Tompkins U.S. Pat. No. 1,530,960 discloses a split sleeve with a beveled upper face mating with a corresponding beveled lower face on a specially prepared casing collar which is used to suspend pipe. No provision for lateral movement is shown.
The J. A. Greenwood U.S. Pat. No. 3,287,035 shows a pipe hanger with a lower ring having a beveled surface seating on a complementary beveled surface in the casing head.
The J. H. Hynes U.S. Pat. No. 3,2889,765 discloses a casing support plate with a lower tapered surface engaging a tapered surface on an outer support flange.